Wellbores are often drilled through a geologic formation for hydrocarbon exploration and recovery operations. Drilling and production operations involve a great quantity of information and measurements relating to parameters and conditions downhole. Such information typically includes characteristics of the earth formations traversed by the wellbore in addition to data relating to the size and configuration of the borehole itself. Often, measurements are made while the wellbores are being drilled. Systems for making these measurements during a drilling operation can be described as logging-while-drilling (LWD) or measurement-while-drilling (MWD) systems, and generally include various sensors carried by a bottom hole assembly (BHA) of a drill string.
At least some of the sensors of an LWD or MWD system may be disposed as near as possible to a downhole end of the BHA to provide measurements representative of the conditions in which a drill bit is operating. Data provided by the sensors can be telemetered uphole to a surface location or to other portions of the drill string by a telemetry tool located in the BHA. The telemetry tool may communicate with a variety of technologies including, but not limited to, mud pulse, electromagnetic, and acoustic technologies. For example, a mud pulser generates pressure fluctuations in fluid flowing through a tubular string, such as drilling fluid or mud flowing through a drillstring. The pressure fluctuations are varied by the mud pulser to modulate data and/or command information on the pressure fluctuations.